Session: 03-02-02: Advanced Manufacturing

Paper Number: 121634

121634 - Nanocrystal Functionalized Natural Fiber-Reinforced Green Composites: Interfacial Modification and Additive Manufacturing 

Natural fiber-reinforced green composites have garnered increasing attention due to their biodegradability and environmental advantages compared to synthetic fibers. Jute fibers are lightweight, cost-effective, readily available, and eco-friendly materials. However, the utilization of jute fibers in composite manufacturing is often constrained by their weak interfacial properties. This limitation necessitates surface modifications, such as chemical treatments and the deposition of nanomaterials, to enhance the fiber-matrix interface properties.

Hydroxyapatite is an inorganic calcium mineral naturally found in human bones and teeth, widely utilized as a biocompatible material in orthopedic surgeries. Despite its significant potential for enhancing structural integrity at interfaces, the deposition of such nanomaterial onto natural fibers is often hindered by its inherent insolubility in non-destructive solvents. Furthermore, the treatment process must address criteria related to fiber degradation.

In this study, we have developed an in-situ process for depositing hydroxyapatite (HAP) nanocrystals onto jute fiber surfaces using wet precipitation synthesis. Subsequently, we fabricated a composite using eco-friendly thermoset matrix materials. To assess the interface properties of the jute fiber-reinforced composites, we conducted nanoindentation and modulus mapping. Furthermore, we have introduced a heat-assisted-curing direct writing additive manufacturing process for creating multilayer biocomposites with intricate geometries. Lastly, we have analyzed the advantages of hydroxyapatite nanocrystals in optimizing the printing process. These benefits include enhancements in thermal conductivity and filament extrusion consistency.

We initially confirmed the in-situ synthesis of hydroxyapatite using Fourier transform infrared spectrometry and subsequently examined the morphological characteristics of the modified fiber through scanning electron microscopy. Our observations revealed that the fiber was densely coated with nanocrystals, forming an approximate layer with a thickness of 2-3 μm. Nanoindentation-based hardness testing along the radial direction exhibited a distinct transition between the fiber-nanocrystal-matrix domains. In quantitative terms, modulus mapping indicated that our thermoset composite's modified fiber exhibited an average modulus of 5.5 GPa, while the epoxy alone showed an average of 4.7 GPa. The incorporation of nanocrystals enhanced the interface to 8.5 GPa. Furthermore, thermal analysis suggested that the modified fiber could reach the required temperature for additive manufacturing approximately three times faster. Extrusion flowrate analysis indicated that the modified fiber improved filament uniformity. Cross-sectional characterization confirmed a high fiber to matrix ratio within the fabricated composite filament. In summary, our surface modification of the fiber enhances the fiber-matrix interface, ultimately benefiting the 3D printing process. This study proposes that HAP-enhanced natural fibers offer an eco-friendly alternative to synthetic fibers and pave the way for the advanced additive manufacturing of sustainable green composites.

Presenting Author: Sirish Namilae Embry-Riddle Aeronautical University

Presenting Author Biography: Sirish Namilae is a Professor and Ph.D. program coordinator in the Aerospace Engineering Department at the Embry-Riddle Aeronautical University. He obtained his MS in Materials Science from the Indian Institute of Science, and a Ph.D in Mechanical Engineering from Florida State University in 2004. He joined the Aerospace Engineering Department at Embry-Riddle in 2014 after ten years of experience in industry (Boeing) and national lab. (ORNL). At ERAU, Dr. Namilae leads the Advanced Materials and Mechanics Group and directs the Composites lab. His research has focused on the areas of composite materials and complex systems & multiscale modeling. He has authored about 100 Journal and Conference publications in these research areas and has advised over thirty graduate students (MS and PhD Thesis). NSF, NIH, DoT, ONR, and NASA have funded his research.